Ankle prosthesis methods

ABSTRACT

Methods of implanting an ankle prosthesis in a subject having an ankle joint in need of replacement.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. application Ser. No. 10/965,070,filed Oct. 14, 2004, which claims the benefit of U.S. ProvisionalApplication Ser. No. 60/510,887, filed Oct. 14, 2003, which is herebyincorporated herein by reference.

FIELD

One embodiment of the present invention relates to an ankle prosthesis.

Another embodiment of the present invention relates to a total anklereplacement prosthesis.

Another embodiment of the present invention relates to an anklereplacement (partial or total) which is adapted, for example: (a) totreat arthritis of the ankle (e.g., ankle arthritis of any cause: afterprevious trauma; primary; malalignment induced; after hindfoot fusion;from recurrent ankle instability; rheumatoid or inflammatory arthritis;gout; local growth; dysplasia; growth plate arrest; avascular necrosis;hemophilia; distant septic event); (b) to revise a fused ankle; and/or(c) to treat trauma. The ankle replacement may be carried out byreplacing one or more joint surfaces of an ankle joint.

Another embodiment of the present invention relates to a method forinserting an ankle prosthesis.

BACKGROUND

In the search for a workable ankle arthroplasty, various designs havebeen tried. As seen below in Table 1, certain published results relatingto conventional total ankle arthroplasty were disappointing for bothpatients and surgeons (the typical clinical series of Table 1 includes20-40 patients followed for an average of five years or less; onlygeneral observations can be made from this data).

TABLE 1 Good-to-Excellent Satisfaction Rates After Total AnkleReplacements - Conventional Designs # of Avg F/U Satisfaction DeviceAuthor/Year Ankles (months) Rate Smith Dini/80 21 27 46% ICLH Goldie/8218 36 60% TPR Jensen/92 23 59 69% Bath & Wessex Carlsson/93 52 60 81%TPR Kumar/88 37 60 52% LCS Buechel/92 40 72 85% Smith Kirkup/85 18 8461% Mayo Kitaoka/96 160 108 19%

As Table 1 reveals, patient satisfaction with conventional, cementedankle implants has ranged from 19 percent to 85 percent (see, e.g., DiniAA, Bassett FH: Evaluation of the early result of Smith total anklereplacement. Clin Orthop 1980; 146:228-230; Goldie I F, Herberts P:Prosthetic replacement of the ankle joint. Reconstr Surg and Traumat1981; 18:205-210; Jensen N C, Kroner K: Total ankle joint replacement: Aclinical follow-up. Orthopedics 1992; 15:236-240; Carlsson A S,Henricson A, Linder L, Nilsson J A, Redlund-Johneur: A survival analysisof 52 Bath-Wessex ankle replacements. The Foot 1994; 4:34-40; Kumar D JR: Total ankle arthroplasty. A review of 37 cases. J Tn Med Assoc 1988;81:682-685; Buechel F F, Pappas M, Iorio U: N J low contact stress totalankle replacement: Biomechanical rationale and review of 23 cementlesscases. Foot Ankle 1988; 8:270-290; Kirkup J: Richard Smith anklearthroplasty. J Roy Soc Med 1985; 78:301-304; Kitaoka H B, Patzer GL:Clinical results of the Mayo total ankle arthroplasty. J Bone Joint Surg1996; 78A: 1658-1664).

It is believed that length of follow-up was a major factor with patientsatisfaction, as patients with longer follow-ups generally had decliningdegrees of satisfaction. As seen below in Table 2, the rates ofradiographic loosening with these conventional implants were quitesubstantial, ranging from 22 percent to 75 percent (see, e.g., GoldieIF, Herberts P: Prosthetic replacement of the ankle joint. Reconstr Surgand Traumat 1981; 18:205-210; Jensen N C, Kroner K: Total ankle jointreplacement: A clinical follow-up. Orthopedics 1992; 15:236-240;Carlsson A S, Henricson A, Linder L, Nilsson J A, Redlund-Johneur: Asurvival analysis of 52 Bath-Wessex ankle replacements. The Foot 1994;4:34-40; Kumar D J R: Total ankle arthroplasty. A review of 37 cases. JTn Med Assoc 1988; 81:682-685; Kirkup J: Richard Smith anklearthroplasty. J Roy Soc Med 1985; 78:301-304; Kitaoka H B, Patzer G L:Clinical results of the Mayo total ankle arthroplasty. J Bone Joint Surg1996; 78A: 1658-1664; Helm R, Stevens J: Long-term results of totalankle replacement. J Arthroplasty 1986; 1:271-277; Bolton-Maggs B G,Sudlow R A, Freeman MAR: Total ankle arthroplasty. A long-term review ofthe London Hospital experience. J Bone Joint Surg 1985; 67B: 785-790).Of note, it is believed that some of the major factors implicated withloosening were: 1) highly constrained designs; and 2) cement fixation(it might have been the use of cement alone, or the combination of theuse of cement to create adequate space for cementation, which was amajor contributing factor to increased loosening rates).

TABLE 2 Radiographic Loosening After Total Ankle Replacement -Conventional Designs # of Avg. F/U Loosening Device Author/Year Ankles(months) Rate ICLH Goldie/82 18 36 22% ICLH Helm/86 14 54 57% TPRJensen/92 23 59 52% Bath & Wessex Carlsson/93 52 60 67% TPR Kumar/88 3760 26% ICLH Bolton- 41 66 32% Maggs/85 Smith Kirkup/85 18 84 39% MayoKitaoka/96 160 108 75%

Further, conventional total ankle arthroplasty has also been plaguedwith unusually high wound problems. The soft tissues around the ankleregion, especially in rheumatoid and elderly patients, provide arelatively thin envelope for arthroplasty containment. Problems withsuperficial and deep infections, resection arthroplasties, attemptedre-implantations or arthrodeses and, occasionally, below-kneeamputations have dampened the enthusiasm of many orthopaedic surgeonsinvolved with conventional total ankle replacement. In this regard, seeTable 3 below, relating to published “long-term” results afterconventional ankle arthrodesis.

TABLE 3 Published “Long-Term” Results After Conventional AnkleArthrodesis Avg Author/ # of F/U Major ** Continued Hindfoot YearPatients (years) Complications Pain DJD Said/78 36 8 24% * >50% Mazur/7912 8 * 25% 100% Morrey/80 41 8 48% 76%  50% Ahlberg/81 41 12 32% 68% 44% Boobyer/81 58 9 21% * * Morgan/85 101 10 10% * * Lynch/88 62 734% * * Glick/96 34 8  6% * *

While somewhat better short term results associated with conventionalimplants have stimulated interest in total ankle replacement, suchconventional implants have shown their deficiencies. For example, oneconventional prosthesis (the AGILITY ankle replacement) has shown anoverall high rate of satisfaction in early follow up but with evidentproblems (see, e.g., Pyevich M T, Saltzman C L, Callaghan J J, Alvine FG: Total ankle arthroplasty: A unique design. Two to twelve-yearfollow-up. J. Bone Joint Surg., Vol 80-A(10):1410-1420, October, 1998;Saltzman C L, Moss T, Brown T D, Buckwalter J A Total Ankle ReplacementRevisited. JOSPT 30(2):56-67, February, 2000; Saltzman C L, Alvine F G,Sanders R W, Gall RJ. Challenges with Initial Use of a Total Ankle.Clinical Orthopaedics and Related Research (Accepted)).

One issue in this regard is the large amount of bone that is typicallyresected during conventional surgery. This creates a problem if revisionis required because the subsequent lack of bone makes revision orconversion to a fusion problematic. The difficulties caused by having toresect a large amount of bone will become more apparent over time aswith longer follow up the need for revision becomes more common.

Another issue with this conventional AGILITY ankle replacement is thelimited range of motion it allows after surgery. It is believed that inapproximately fifty percent of the cases the patient's plantarflexioncontracture remained with patients not being able to dorsiflexsignificantly beyond neutral position.

A second conventional prosthesis (the STAR), while believed to notrequire as much bone resection, has articular contact surfaces that areflat in the medial-lateral direction, thus making edge loading necessarywhen resisting the varus/valgus loads imposed upon the ankle duringordinary ambulation (see, e.g., Kofoed H, Danborg L: Biological fixationof ankle arthroplasty. Foot 1995; 5:27-3 1; Kofoed H, Toben S: Anklearthroplasty for rheumatoid arthritis and osteoarthritis: Prospectivelong-term study of cemented replacements. J Bone Joint Surg 1998;80B:328-332).

Further still, additional papers include the following: Morgan C D,Henke J A, Bailey R W, Kaufer H: Long-term results of tibiotalararthrodesis. J Bone Joint Surg 1985; 7A:546-550; Glick T M, Morgan D D,Myerson M S, Sampson T O, Mann J A: Ankle arthrodesis using anarthroscopic method: Long-term follow-up of 34 cases. Arthroscopy 1996;12:428-434; Money B F, Wiedeman G P: Complications in long-term resultsof ankle arthrodeses following trauma. J Bone Joint Surg 1980;62A:777-784; Ahlberg A, Henricson A S: Late results of ankle fusion.Acta Orthop Scand 1981; 52:103-105; Mazur J M, Schwartz E, Simon S R:Ankle arthrodesis; long-term follow-up with gait analysis. J Bone JointSurg 1979; 61A:964-975; Boobbyer G N: The long-term results of anklearthrodesis. Acta Orthop Scand 1981; 52:107-110; Said B, Hunka L, SillerT N: Where ankle fusion stands today. J Bone Joint Surg 1978;60B:211-214; Lynch A F, Bourne R B, Rorabeck C H: The long-term resultsof ankle arthrodesis. J Bone Joint Surg 1988; 70B:113-116.

Moreover, issued patents include the following: U.S. Pat. No. 6,183,519,entitled Ankle Prosthesis; U.S. Pat. No. 5,957,981, entitled AdjustableProsthesis Joint; U.S. Pat. No. 5,824,106, entitled Ankle Prosthesis;U.S. Pat. No. 5,800,564, entitled Ankle Prosthesis With AngleAdjustment; U.S. Pat. No. 5,766,259, entitled Total Ankle Prosthesis AndMethod; U.S. Pat. No. 5,728,177, entitled Prosthesis With Foam BlockAnkle; U.S. Pat. No. 5,312,216, entitled Artificial Joint Prosthesis;U.S. Pat. No. 5,156,630, entitled Ankle Joint Prosthesis Fixable In MoreThan One Orientation; U.S. Pat. No. 5,019,109, entitled Multi-AxialRotation System For Artificial Ankle; U.S. Pat. No. 4,778,473, entitledProsthesis Interface Surface And Method Of Implanting; U.S. Pat. No.4,755,185, entitled Prosthetic Joint; U.S. Pat. No. 4,659,331, entitledProsthesis Interface Surface And Method Of Implanting; U.S. Pat. No.4,470,158, entitled Joint Endoprosthesis; U.S. Pat. No. 4,442,554,entitled Biomechanical Ankle Device; U.S. Pat. No. 4,360,931, entitledProsthetic Ankle; U.S. Pat. No. 4,340,978, entitled New Jersey MeniscalBearing Knee Replacement; U.S. Pat. No. 4,309,778, entitled New JerseyMeniscal Bearing Knee Replacement; U.S. Pat. No. 4,166,292, entitledStressed Reinforced Artificial Joint Prosthesis; U.S. Pat. No.4,156,944, entitled Total Ankle Prosthesis; U.S. Pat. No. 4,069,518,entitled Total Ankle Prosthesis; U.S. Pat. No. 4,021,864, entitled AnkleProsthesis; U.S. Pat. No. D242,957, entitled Total Ankle Prosthesis;U.S. Pat. No. 3,987,500, entitled Surgically Implantable Total AnkleProsthesis; and U.S. Pat. No. 3,975,778, entitled Total AnkleArthroplasty.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1E show an ankle prosthesis according to an embodiment of thepresent invention;

FIGS. 2A-2K show implantation of an ankle prosthesis according to anembodiment of the present invention; and

FIG. 3 shows instrumentation according to another embodiment of thepresent invention.

Among those benefits and improvements that have been disclosed, otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingfigures. The figures constitute a part of this specification and includean illustrative embodiment of the present invention and illustratevarious objects and features thereof.

SUMMARY

In an embodiment, a fixed-bearing ankle prosthesis includes a tibialcomponent for attachment to a tibia, wherein the tibial component hasfirst and second surfaces, and a talar component for attachment to atalus, wherein the talar component has first and second surfaces andmedial and lateral edges. At least a portion of the first surface of thetibial component is configured to be disposed adjacent the tibia. Atleast a portion of the first surface of the talar component isconfigured to be disposed adjacent the talus. At least a portion of thesecond surface of the tibial component and at least a portion of thesecond surface of the talar component contact one another directly toform an articulation interface between the tibial component and thetalar component. The articulation interface includes a bicondylargeometry such that the second surface of the tibial component defines amedial condylar facet and a lateral condylar facet and the secondsurface of the talar component includes a medial condyle and a lateralcondyle. The medial and lateral condylar facets of the tibial componenthave concave circular arc cross-sections extending in a medial-lateralplane. The medial condyle of the talar component has a first singleradius in the medial-lateral plane that defines a convex circular arccross-section continuously extending, in the medial-lateral plane, fromthe medial edge of the talar component to a concave central portion ofthe talar component second surface separating the medial and lateralcondyles. The lateral condyle of the talar component has a second singleradius in the medial-lateral plane that defines a convex circular arccross-section continuously extending, in the medial-lateral plane, fromthe lateral edge of the talar component to the concave central portionof the talar component second surface. The concave circular arccross-section of the medial condylar facet of the tibial component has aradius in the medial-lateral plane larger than the first radius. Theconcave circular arc cross-section of the lateral condylar facet of thetibial component has a radius in the medial-lateral plane larger thanthe second radius.

In another embodiment, a fixed-bearing ankle prosthesis includes atibial component and a talar component. The tibial component includes atibial attachment surface and a tibial articulating surface. The talarcomponent includes a medial edge, a lateral edge, a talar attachmentsurface, and a talar articulating surface, the talar articulatingsurface directly contacting the tibial articulating surface. The tibialarticulating surface includes a medial concave condylar facet and alateral concave condylar facet, each condylar facet having a radius ofcurvature in a medial-lateral plane that defines a respective circlearc, the facets separated from one another by a convex central portion.The talar articulating surface includes a medial convex condyle thatunderlies the medial condylar facet, and a lateral convex condyle thatunderlies the lateral condylar facet. The condyles are separated fromone another by a concave central portion that underlies the tibialconvex central portion. The medial condyle of the talar component has afirst single radius of curvature in the medial-lateral plane thatdefines a convex circular arc cross-section continuously extending, inthe medial-lateral plane, from the medial edge of the talar component tothe concave central portion of the talar articulating surface. Thelateral condyle of the talar component has a second single radius ofcurvature in the medial-lateral plane that defines a convex circular arccross-section continuously extending, in the medial-lateral plane, fromthe lateral edge of the talar component to the concave central portionof the talar component second surface. The medial condyle radius ofcurvature is smaller than the medial condylar facet radius of curvature,and the lateral condyle radius of curvature is smaller than the lateralcondylar facet radius of curvature.

DETAILED DESCRIPTION

Detailed embodiments of the present invention are disclosed herein;however, it is to be understood that the disclosed embodiments aremerely illustrative of the invention that may be embodied in variousforms. In addition, each of the examples given in connection with thevarious embodiments of the invention are intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

In one embodiment an ankle prosthesis according to the present inventionminimizes edge loading by using bicondylar articular geometry whichenhances varus/valgus stability while maintaining an appropriatelycentral load distribution within the prosthesis. In this regard, it isbelieved that in combination with adequate bone coverage of the resectedbones by the prosthesis, an appropriately central load distributionwould minimize prosthesis subsidence into the bone (by minimizing bonestress). Such a bicondylar geometry may allow the achievement ofvarus/valgus stability by shifting the joint compressive load centermedially or laterally upon the joint contact surface, but prevents thejoint compression load center from reaching the edge of the contactsurface. An appropriate mechanism for varus/valgus stability mayincorporate the shifting of the joint contact load from the medial tothe lateral bicondylar surface for moderate varus/valgus loads andaugmenting this stability mechanism with tensile loads in the collateralligaments spanning the ankle joint. To produce collateral ligamentloads, it may be necessary to stretch the ligaments and hence allow theopening of either the medial or the lateral condylar surfaces. By use offull radii of curvature of the medial and lateral bicondylar surfacesthis embodiment may allow varus/valgus angulation to the extent ofapproximately, for example (which example is intended to be illustrativeand not restrictive) three to five degrees, while maintainingessentially full central contact within either the medial or lateralcondyle. This allows the required contact load shifting and stretchingof the appropriate collateral ligament without significant edge loading.In another example (which example is intended to be illustrative and notrestrictive), the angulation may be one to ten degrees.

In another embodiment an ankle prosthesis according to the presentinvention utilizes articular surface(s) with conical shape(s) whichoperate to couple the flexion/extension and inversion/eversion (it isbelieved that a contributing factor to a stable gait and properfoot/ground contact pattern is the coupling between theflexion/extension mechanism and the inversion/eversion motion normallypresent in the ankle joint).

In another embodiment an ankle prosthesis according to the presentinvention utilizes a design that: (a) in extreme dorsiflexion provides amaximized plantarflexion moment arm; and (b) in extreme plantarflexionprovides a maximized dorsiflexion moment arm. This may be accomplishedby choosing appropriate radii of curvature for one or more articularsurfaces (e.g., so as to allow approximately, for example (which exampleis intended to be illustrative and not restrictive), two or threemillimeters of anterior/posterior translation of the tibial and talarcomponents). In another example (which example is intended to beillustrative and not restrictive), one to five millimeters ofanterior/posterior translation of the tibial and talar components may beprovided.

In another embodiment an ankle prosthesis utilizes a design thatprovides for the “contact point” or center of contact pressure to moveanteriorly with dorsiflexion and posteriorly with plantarflexion (e.g.,to achieve an acceptable range of motion by allowing the ankle joint tofollow the biomechanical principle that, in extreme positions of motion,the muscle group with the more favorable moment arm is that group whichopposes the extreme motion.

Of note, conventional ankle joint prostheses typically attempt toachieve low contact stress and low wear by using either fully congruentcontact surfaces, such as found in mobile bearings, or so calledflat-on-flat designs that provide cylindrical articulating surfaces.While various embodiments of the present invention provide the abovedescribed bicondylar geometry, the above described coupledflexion/extension and inversion/eversion motion and the above describedanterior/posterior translation of the center of the joint contactsurface, an additional embodiment combines these three features in sucha way so as to avoid either fully congruent articular surfaces or lineto line contact articular surfaces (i.e., an embodiment of the presentinvention utilizes articular surfaces that are not fully congruent inthe anterior/posterior direction or the medial/lateral direction). Moreparticularly, the surface geometry in this embodiment is comprised ofcircle arcs. These arcs form both the medial/lateral andanterior/posterior contours of the tibio-talar articulating surface.Moreover, in the medial/lateral direction, these radii overlie a conicalsection. In one example (which example is intended to be illustrativeand not restrictive) a ratio of the talar component radii of curvatureof both medial and lateral bicondylar surfaces, in the medial/lateraldirection, may be between 92% and 96% of the corresponding tibialcomponent radii of curvature of both medial and lateral bicondylarsurfaces (i.e., the medial-lateral plane radii of the circular arccross-sections of the tibial component are larger than correspondingradii of the circular arc cross-sections of the talar component). Inanother example (which example is intended to be illustrative and notrestrictive) the corresponding ratios for these two articulatingcondylar surfaces in the anterior/posterior direction may be between 85%and 96% (i.e., the anterior-posterior radii of the circular arccross-sections of the tibial component are larger than correspondingradii of the circular arc cross-sections of the talar component).

Of further note, an ankle joint is composed of three articulatingsurfaces: tibial/talar articulation, medial malleolus/talararticulation, and lateral malleolus/talar articulation. Conventionalankle prostheses typically do not allow the surgeon to choose, at thetime of surgery, which of these three joint surfaces will be replaced(it is believed that some conventional prostheses provide only ahemiarthroplasty on the medial and lateral sides). This is a potentialsource of impingement or pain from articulation of the arthritic jointsurface against the metal surface. While it is true that this is notnecessarily a concern in all the patients, many of whom may have minimalarthritic changes in the medial or lateral gutters, it may be desirableto provide flexibility at the time of surgery according to an embodimentof the present invention (e.g., so that if the surgeon identifiesarthritis in the medial or lateral gutter, a total joint replacementrather than hemiarthroplasty can be performed).

In another embodiment an ankle replacement, implant procedure, andimplant instrumentation are provided which: 1) do not sacrifice too muchbone (which excess sacrifice could make revision of the implant and/orconversion to a fusion difficult); 2) do not place the implant onrelatively weak bone (which could encourage subsidence,); 3) do notallow excessive loosening of the implant from poor fixation; and 4) donot result in a significant incidence of wound problems.

In another embodiment an ankle prosthesis may include an element (e.g.,a button with an articular surface (e.g., a spherical or spheroidalshaped articular surface)) that can be placed on either or bothmalleolar articulating surfaces to form an articular interface withlateral surfaces of the talar component (or any biomechanical axis). Inone example (which example is intended to be illustrative and notrestrictive), this feature may provide the surgical option ofresurfacing one or both of the medial and lateral gutters (e.g., whichlateral gutter may comprise a lateral fibula and talar articularsurface)).

Referring now to FIGS. 1A-1E, an ankle prosthesis according to anembodiment of the present invention is shown.

FIG. 1A shows a side view of a talar component of the ankle prosthesis.The talar component has a concave first surface that is configured to bedisposed adjacent the talus and a second surface which articulates witha tibial component.

FIG. 1B shows a view of the talar component from its first surface.

FIG. 1C shows a partial medial-lateral cross-section of the tibial(upper) and talar (lower) components. The central portion of the talarcomponent second surface is concave, and a central portion of the tibialcomponent second surface, which separates the medial and lateralcondylar facets and which overlies the talar component central portion,is convex.

FIG. 1D shows a side view of a tibial component of the ankle prosthesis.The tibial component has a convex first surface that is configured to bedisposed adjacent the tibia and a second surface which articulates withthe talar component.

FIG. 1E shows a view of the tibial component from its second surface.

Referring now to surgical methods (and corresponding instrumentation)which may be used to implant the ankle prosthesis, it is noted that theinvention may be utilized, for example, in the context of an anteriorapproach, a lateral approach, a combined lateral and medial approach, ora combination of a lateral and anteromedial approach.

In any case, referring now to FIGS. 2A-2K, implantation steps of anankle prosthesis according to an embodiment of the present invention maybe as follows:

-   -   1) Do a lateral approach, fibular osteotomy and exposure of the        joint.    -   2) Attach two pins to the tibia and one to the medial talus.    -   3) With use of fluoroscopy, adjust the alignment of the tibia        and lock this so that the shaft of the tibia is parallel to the        radiopaque rod in the alignment jig.    -   4) Strap the foot on the clear foot plate.    -   5) Adjust the cutter pivot assembly to allow a side cutting        instrument (e.g., drill) to arc the outer surface of the tibial        component from the tibia. This device allows proximal-distal        adjustment and anterior/posterior adjustment. A set of pivot        guides may be associated with each size of implant, that is, for        a small implant there may be a smaller radius of curvature. The        guides may also have stops to avoid overreaching with the side        cutting bit.    -   6) After the appropriate amount of bone is remove from the tibia        (e.g., enough to allow proper positioning of the foot—with the        calcaneus in neutral position) attention is directed to the        talar side.    -   7) The foot plate is positioned so the plantar aspect of the        entire foot is perpendicular to the tibia. The translucent plate        on which the foot is secured allows the surgeon to be absolutely        sure the heel and metatarsals all are in contact.    -   8) The superior dome of the talus is then side cut with the same        pivot guide assembly.    -   9) Trial spacers are placed to ensure parallelism of the cuts,        and no overtensioning of the deltoid.    -   10) The spacers may have lateral slots for drilling the ridge        holes and overhangs through which pins are temporarily placed to        secure the guide for the ridge holes.    -   11) One or two lateral-medial ridge hole(s) are drilled adjacent        to the exposed cut surface of the distal tibia and one or two        others are drilled in the superior surface of the proximal        talus.    -   12) Trial tibial and talar components are placed and again the        deltoid tightness is assessed. If needed more bone is removed        with the side cutting instrument (e.g., drill) and pivot guide.    -   13) Occasionally, the surgeon may make an anteromedial incision        to remove bone from the medial side of the joint (the surgeon        may decide to use the same implant with a medial and/or lateral        overhang to the talar component). The surgeon may also decide to        use a cemented polyethylene button on the medial side of the        fibula.    -   14) The lateral side is then adjusted in a superior/inferior        direction to maintain ligament tension on the calcaneal-fibular        ligament.    -   15) The lateral fibula is fixated with standard orthopaedic        hardware such as a plate and/or screw, tension band technique or        intramedullary device.

In another embodiment in connection with step (2) above, the surgeon mayhave the option of not only placing a pin in the talus but also in thecalcaneus.

In another embodiment, step (7) above may be combined with the step (4)above, such that step (4) includes both elements (i.e., strapping thefoot on the clear foot plate and positioning the foot plate.

Other embodiments of the present invention may include the followingsurgical methods and corresponding instrumentation:

1. Anterior Approach

A. Technique

In the anterior approach according to one embodiment a straight incisionmay be used (e.g., to minimize wound problems). The dissection may becarried through the extensor hallucis longus sheath with the EHL tendonretracted medially and the neurovascular bundle retracted laterally(this leaves the blood supply to the extensor digitorum brevis intactfor the possible use in a flap in case of a wound problem).

The tibial bone cut may be made from a cutting block which may be setessentially parallel to the floor when the foot is in a plantigradeposition on both the AP view and perpendicular to the midlongitudinalaxis of the tibia on the lateral view. Fluoroscopy may be used todetermine the position of the cutting block so that a minimal amount ofbone will be resected with the proper alignment. In one example (whichexample is intended to be illustrative and not restrictive) somepatients may be treated using a guide system based on the plane of thesole of the foot that will allow cuts to be made parallel to this planein the tibia and the superior portion of the talus. For the top portionof the talar cut an extension to the tibia cutting block may be used.The front and back or the side cuts may be performed next. For the frontand back cuts, a different cutting block may be attached to the talus.For the side cuts, the same cutting block or a third cutting blockreferenced to the talus may be used. Once the cuts are completed, boththe tibia and talar trial components may be placed and range of motionand ligament laxity/tightness determined. Finally, ligament balancingmay be performed to help insure proper ligament tension both mediallyand laterally without excessive laxity or tightness in the ligaments. Inanother example (which example is intended to be illustrative and notrestrictive) instrumentation stops may be available for some or all cutsused and/or appropriate design features may be incorporated to make itdifficult to cut beyond a desired range (e.g., in the area of theposterior aspect of the tibia where injury to tendons and nerves arepossible; tendon lacerations from such cuts have occurred in total anklereplacements).

B. Instrumentation

The instrumentation may include a cutting block for the distal tibialcut attached to a long rod secured to the proximal leg. This block maybe designed to permit fine adjustments superior-inferior, mediallateral, and may have a capture mechanism for the saw blade. The cuttingblock may be placed under fluoroscopic control. In one example (whichexample is intended to be illustrative and not restrictive) 2 pins inthe tibia may be used for fixation. In this case, the first pin may beplaced with consideration of internal-external rotation. Afterward thevarus-valgus position may be determined, for example, by fluoroscopicimaging and/or from the plane of the sole of the foot and the second pinmay be placed. Next the extension-flexion position for the lateral X-rayimage may be determined and when the position of the block permits a cutperpendicular to the mid-longitudinal axis of the tibia the height ofthe tibial rod may be secured at the level of the proximal tibia. Theheight of the cut may be fine-tuned at the cutting block. The AP viewmay be repeated and the medial-lateral extent of the cut may thenadjusted and locked in. The saw may have a stop to reduce possibility ofinjury to vital posterior soft tissue structures. After this cut ismade, the talus may be positioned in all three planes and a blockextension may be used to remove the superior surface.

The instrumentation may include right and left guides for making theposterior, anterior, and medial/lateral cuts on the talus. In addition,the invention may employ a guide for cutting the corresponding surfacesof the malleoli and placing a slot for the buttons (e.g., poly buttons).

2. Lateral Approach

A. Technique

The advantages of this approach (relative to the anterior approach) mayinclude: 1) less bone resection; 2) essentially complete access to thelateral joint space; 3) ability to perform a controlled release ofchronically tight posterior ankle and/or subtalar joint ligaments; 4)decreased risk of tendon and/or nerve lacerations with the ability toplace retractors on the posterior tibia; and 5) likely decreasedincidence of wound complications. In addition, this lateral approachoffers the possibility to perform one or more curved cuts and/or one ormore flat cuts close to a curved cut on both of these articular surfaces(i.e., the distal tibial and proximal talar). Such curved cuts and/orone or more flat cuts close to a curved cut may aid in minimizing boneresection, thereby retaining the periankle bone stock (which is aparticularly strong bone for stress transfer). Curved or nearly curvedsurfaces with minimal bone resection should allow for a greater area ofcoverage of this stronger bone.

To have access to the ankle, the lateral side of the fibula isosteotomized. The distal fibular fragment may be reflected posteriorly,after incising the anterior talofibular ligament (which may be repairedat the end of the procedure). The fibula osteotomy may be later fixedwith screws and/or plate and/or other fixation at the end of theprocedure. In one example (which example is intended to be illustrativeand not restrictive) bone cuts may be made by an oscillating curved sawblade for the curved talar and/or tibial cuts or alternatively flat cutsbut with minimal bone resection. These cuts may be aligned by bonylandmarks and/or off an alignment guide. K wires may be placed andchecked fluoroscopically and used to fix the alignment guides and/orguide the bone cuts. The described approach may give access to thelateral joint surface of the talus and the medial aspect of the lateralmalleolus. One or both of these surfaces may be prepared for resurfacingfrom this approach.

To gain adequate access to the medial joint surface when a transfibularapproach is used, a separate incision may be made on the anteromedialside of the ankle joint. Through the anteromedial and lateral incisionsany anterior osteophytes may be removed. This approach may allowresurfacing of the medial aspect of the talus, the lateral aspect of themedial malleolus and controlled cutting of the tibia and talus from thelateral side. From the anteromedial incision either an osteotome may beplaced along the superior medial gutter into the tibia or pins may beused to block the progress of the saw blade and prevent cutting themedial malleolus when the cuts are made from lateral to medial. Ifcurved cuts are used the extent of the curve anteriorly and posteriorlymay likely be slightly more than that of the ankle prosthesis. From thelateral approach one or more small slot cuts for initial fixation of theimplant(s) may be made. In one example (which example is intended to beillustrative and not restrictive) these slot cuts(s) may be done with adrill directly through the joint line to simultaneously produce a slotinto the tibia and talus. This may correspond to a small peg on thetibial and/or talar trials and/or implants to guide insertion andmaintain alignment. From the medial approach, when needed, the surgeonmay prepare the medial aspect of the talus and/or the lateral aspect ofthe medial malleolus for implant fixation.

B. Instrumentation

If curved cuts are to be used, an oscillating saw, drill, bun, and/orrouter may, in one example (which example is intended to be illustrativeand not restrictive), be employed to make such cut(s). On the tibialside, pin(s) may be placed under fluoroscopic guidance to define theplane of the cut. In the AP projection, this pin may be placed to lockin the varus-valgus and internal-external rotation position of thetibial tray. In one example (which example is intended to beillustrative and not restrictive) a cutting saw that is curved with anattached guidance slot for the pin may be used. For positioning of thetalar cut a pin may be used perpendicular to the side of the talus orsomewhat off this perpendicular according to the alignment of the cone,or the cut may be made off the pin already inserted in the tibia afterthe talus has been held in the correct amount of varus-valgus andinternal-external rotation by the surgical team. For the tibial andtalar guides an alignment cutting block may be used. In one example(which example is intended to be illustrative and not restrictive) thecuts for the pegs may be made with the drill, router, or small saw tosimultaneously make the slots for the talar and tibial components. Thismay be done in one of many ways known to those of ordinary skill in theart. Trials with undersized pegs for the slots can then be applied.Trials may be used to judge alignment, adequate range of motion withoutimpingement and ligament tension.

A separate guide for the medial and lateral cuts on the talus may beused to assure proper width of the talus to fit the implant. In oneexample (which example is intended to be illustrative and notrestrictive) it is likely that after the top talar cut, the lateral cutwill be made on the talus. A guide on the top of the talar may then beused to make a corresponding medial cut through the anteromedialincision, and lateral cut through the transfibular approach. This may bedone in a reverse order. The medial cut may be made as described for theanterior technique. The lateral cut may be made with a cutout along thelateral joint surface (e.g., that is cleared by a side cutting drill bitwith a depth stop). The medial surface of the lateral malleolus may beprepared as a standard patellar resurfacing to allow a cemented button(e.g., poly button) to be placed. The lateral surface of the medialmalleolus may be prepared with a saw cut and placement of a slot for thebutton peg.

Referring now to FIG. 3, instrumentation according to another embodimentof the present invention is shown.

In another embodiment the instrumentation may be made to align the cutsaccording to bony landmarks and/or fluoroscopic control.

In another embodiment the guides for the cutting may be fixed to anexternal fixator, and/or be fixed directly to the bone, and/or be basedon a guidance system (e.g., from the plane of the sole of the foot). Theaforementioned configurations may be used for purposes of overallalignment and stability.

In another embodiment some or all of the instrumentation may be made soas to be used on the right and left ankles (i.e., all of theinstrumentation may be made so as to be used on the right and leftankles or there may be some separate instrumentation for the rightand/or left sides).

In another embodiment an ankle replacement may be shaped to conform tothe curvilinear shape of the bones which comprise the ankle.

In another embodiment curved as well as straight cuts may be used toprepare the bony surfaces for implantation (e.g., in order to sacrificeless bone as compared to straight cuts alone).

In another embodiment an ankle replacement may be inserted through alateral and medial approach (the implant may, of course, be insertedusing another approach (e.g., an anterior approach).

In another embodiment revision tibial and talar implants with threaded(e.g., male) fixation peg(s) on the surface facing the bone may be usedwith a variety of differently sized (e.g., length, width and/or shape)interchangeable (e.g., female) fixation devices.

In another embodiment an ankle replacement may be composed of metal,ceramic, an ultra high molecular weight polyethylene plastic and/or atantalum mesh.

In another embodiment an ankle prosthesis is provided in which at leastone component (e.g., a tibial component) includes a polymer plasticbearing surface (e.g., ultra high molecular weight polyethylene(UHMWPE)), wherein the bearing surface is integrally attached to a metaland/or ceramic backing plate. This plate may contain an appropriatesurface for interfacing with and attaching to bone. Further, thisinterface surface may be of a porous nature to allow bone ingrowth.Further still, malleolar components may be universal. These componentsmay use mechanical attachment with a bone-cement interface and/or anappropriate porous metal backing to allow fixation to the bone.

In another embodiment the polyethylene articular surfaces may beproduced by direct compression molding (a process that provides enhancedaging resistance and wear resistance).

In another embodiment a method of attachment between the polyethylenebearing surface and the metal backing may utilize direct compressionmolding of the articular surface onto the metal backing (withinterlocking provided by any of the methods known to those of ordinaryskill in the art (e.g., undercuts and/or porous surface penetration).

In another embodiment a system of implant(s) to accommodate the specialrequirements of revision surgery (and/or conversion to a fusion) isprovided. Revision problems such as, for example, subsidence and boneloss, subluxation and possible dislocation may be addressed by thisembodiment. In the event such problems should occur (or to revise othertotal ankle replacements), revision implants may be provided. Fordislocation or subluxation the ability to revise the bone cuts so thejoint will not sublux may be necessary and provided for. In thisinstance (as well as the instance of significant bone loss),augmentation of bone stock may be allowed for. The use of bonesubstitutes and/or bone graft with bone substitutes may be possible.Design features such as metal peg(s) screwed into the revisionprosthesis and/or slot(s) and/or fin(s) may be used. These designfeatures may articulate with the patient's bone to assist in fixation(e.g., of the bone graft to the patient's bone and the implant).

In another embodiment the present invention lends itself directly tocomputer navigational and/or robotic implantation. For example, use of anavigational system may help insure proper alignment of the foot versusthe tibia in judging things such as heel valgus and foot position versusthe tibia. Further, it is noted that an embodiment of the presentinvention may require cutting mechanism(s) be attached to the tibia in away that allows direct (e.g., through the fixator setup) distraction ofthe joint with the cutting guides attached to the fixator.

In another embodiment, an element of the present invention may be acurved or nearly curved shape on the bone side of the tibial and talarcomponents. These may be curved cuts or nearly so using a series offlats cuts to take minimal bone.

In another embodiment, an element of the present invention may be theexternal fixating jig for alignment and the tibial and talar bone cutswhich are used for the purpose of alignment.

In another embodiment, an element of the present invention may be thefixation of the whole jig to the tibia as well as to the foot.

In another embodiment, the prosthesis may include a medial-lateralridge.

In another embodiment, the prosthesis may maintain stability with littleor no edge evolving.

While a number of embodiments of the present invention have beendescribed, it is understood that these embodiments are illustrativeonly, and not restrictive, and that many modifications may becomeapparent to those of ordinary skill in the art. For example, the stepsdescribed in connection with the surgical procedures (and/or anyassembly/manufacturing) may be carried out in any desired order, somesteps may be omitted, and/or other steps may be added. Further, some ofthe instrumentation described herein may not be utilized and/oradditional instrumentation may be employed. Further still, the ankleprosthesis may include left sided and right sided components (e.g.,tibial and talar components). Of note, such left sided and right sidedcomponents may be used, in one embodiment, due to a conical component ofthe articular geometry. Further still, the apparatus (and/or itscomponents) may, of course, have any desired dimensions (e.g., for anydesired patient—man, woman or child). Further still, the apparatus(and/or its components) may be provided in a “line” or “family” ofdevices (e.g., small, medium and large; adult, child; male, female).Further still, the apparatus (and/or its components) may be provided instandard sizes.

1. A method of implanting an ankle prosthesis in a subject having anankle joint in need of replacement, the ankle joint including a distaltibia end, a fibula, and a talus, the method comprising: providing afixed-bearing ankle prosthesis comprising a tibial component and a talarcomponent, wherein: the tibial component comprises a convex tibialattachment surface defined by a circle arc and a tibial articulatingsurface; the talar component comprises a medial edge, a lateral edge, aconcave talar attachment surface defined by a circle arc, and a talararticulating surface, the talar articulating surface directlycontactable with the tibial articulating surface; the tibialarticulating surface comprises a medial concave condylar facet and alateral concave condylar facet, each condylar facet having a radius ofcurvature in a medial-lateral plane that defines a respective circlearc, the facets separated from one another by a convex central portion;the talar articulating surface comprises a medial convex condyle thatunderlies the medial condylar facet, and a lateral convex condyle thatunderlies the lateral condylar facet, the condyles separated from oneanother by a concave central portion that underlies the tibial convexcentral portion; the medial condyle of the talar component has a firstsingle radius of curvature in the medial-lateral plane that defines aconvex circular arc cross-section continuously extending, in themedial-lateral plane, from the medial edge of the talar component to theconcave central portion of the talar articulating surface; the lateralcondyle of the talar component has a second single radius of curvaturein the medial-lateral plane that defines a convex circular arccross-section continuously extending, in the medial-lateral plane, fromthe lateral edge of the talar component to the concave central portionof the talar component second surface; the medial condyle radius ofcurvature is smaller than the medial condylar facet radius of curvature;and the lateral condyle radius of curvature is smaller than the lateralcondylar facet radius of curvature; performing an osteotomy of thefibula to gain lateral access to the distal tibia end and the talus;distracting the ankle joint; making a concave cut in the distal tibiaend corresponding to the convex curve of the tibial attachment surfaceto create a tibial cut end; making a convex cut in the taluscorresponding to the concave curve of the talar attachment surface tocreate a talar cut end; fixing the tibial attachment surface of thetibial component to the tibial cut end; fixing the talar attachmentsurface to the talar component to the talar cut end; approximating therespective articulating surfaces of the tibial component and the talarcomponent so that they contact one another; and refixating the fibula.